Early Warning System Alerts High-Risk Patients to Heart Attack

May 05, 2010

An implantable pacemaker-sized monitor that sounds an alarm when it senses abnormal changes in the heart's electrical activity is proving an effective early warning system for patients at high risk of a heart attack or dangerous plaque rupture, according to data presented today at the Society for Cardiovascular Angiography and Interventions (SCAI) 33rd Annual Scientific Sessions.

Preliminary data from two studies showed that the novel device successfully warned patients of a heart attack or acute coronary syndrome by detecting the electrocardiographic (ECG) changes that take place when an arterial blockage causes a dangerous shortfall in blood and oxygen to the heart muscle (ischemia). One immediate benefit of the ischemia monitor is that it helps patients arrive at the emergency room within minutes of receiving an alert, rather than waiting for hours, as is more typical.

"Despite our best efforts, it still often takes two to three hours before patients come to the emergency room when they have heart attack symptoms," said C. Michael Gibson, MD, FSCAI, director of clinical research for Beth Israel Deaconess Medical Center in Boston. "Patients may think their pain comes from heartburn or spasm of the esophagus, or they may be in denial about having a heart attack and just wish the symptoms would go away. This device is tough to ignore, and it provides patients with greater certainty."

The AngelMed ischemia monitor is implanted in the chest and connects to a pacemaker lead (a wire that attaches to the heart). It compares current data from the patient's heart to prior data collected when the heart was normal. Using this comparison it can instantly recognize abnormal shifts in the ST segment, a portion of the electrocardiogram that doctors use to diagnose a heart attack or acute coronary syndrome. Upon sensing an abnormal ST-segment change, the implanted device buzzes inside the patient's chest and an external pager sounds an alert.

The two new studies included 37 patients who were at high risk for a heart attack. After implantation of the early-warning ischemia monitor, patients were followed-up for an average of 1.5 years. During that time, the monitor accurately detected early signs of a heart attack in four patients and acute coronary syndrome in another four. There were three false-positive alerts, one because of a programming error and two because the patient developed a specific abnormal heart rhythm.

There were no undetected heart attacks, and no patients died during follow-up or developed Q-waves on the electrocardiogram, a serious finding that indicates that a heart attack has caused full-thickness damage to an area of heart muscle. In part, that may be because patients arrived at the emergency room an average of 19.5 minutes after an alarm sounded, markedly reducing the time it took to open the blocked artery.

"Every hour you delay getting to the hospital increases the odds of dying," Dr. Gibson said. "We think this device may make a difference in outcomes."

An ongoing Phase II study will enroll up to 1,000 high-risk patients, with the aim of documenting the effect of the ischemia monitor on survival and other key outcomes.

AngelMed provided funding for the studies. Dr. Gibson also receives research support from the company.

The study, "Initial Results Using an Implantable ST-Segment Monitoring System that Detects and Alerts Patients To Coronary Plaque Rupture and Ischemia," will be presented at a poster session on Wednesday, May 5, 12:30 pm to 5:00 pm.